Example uses of capacity terminology
Here is an example of how terms are used in Storage Modeller.
Planning: The storage administrator, is planning the configuration of their storage system. They will be using compression and deduplication on all
volumes and plans on a data reduction savings of 3:1 for their data. They are creating one pool for their entire system and would like to ensure a
provisioning limit of 2.5:1. This means the other users of this system cannot create volumes if this would exceed a
provisioned capacity of more than 2.5 times the usable capacity of the pool/system. With a planned
data reduction savings of 3:1, they know this is below the effective capacity of 300 TiB (100 TiB usable
capacity * 3:1 data reduction).
Figure 77 on page 80.
Configuring: The storage operator, sees there is 100 TiB of usable capacity in the pool they were given. They
create 200 compressed/deduped volumes, each of which is 1 TiB in size for their VM environment resulting in 200 TiB of provisioned capacity. The
pool and system report back that they have a 2:1 over-provisioned ratio. It also reports that there is initially 0.2 TiB of
used capacity. Drilling down, they see this is from overhead capacity that is used by the system for these
volumes. See Figure 77 on page 80.
Monitoring: A while after being in production, the storage administrator monitors the used capacity to ensure
that it does not go over the 90% threshold they created. They also monitor their data reduction savings to ensure they are seeing the
compression/dedupe rates they expected. From the GUI, they see these details shown in
Figure 77 on page 80:
▪50 TiB of written capacity were written to the volumes by the host system and mirroring environment before compression.
▪Their usable capacity has 50 TiB of used capacity and 50 TiB
available capacity. This leads to,
– A thin-provisioning savings of 50 TiB or 25% (200 TiB
provisioned capacity - 150 TiB written capacity)
– A data reduction savings of 100 TiB or 66% (50 TiB
used capacity - 100 TiB written capacity).
▪This results in a total capacity savings of 160 TiB or 75%.
Figure 77 Example of Usable Capacity, Effective Capacity and Capacity Savings.